Methods for introducing samples into an apparatus for the analysis of vapors and vapor-entrained materials, such as gas chromatographs and ion mobility spectrometers, have hitherto been (1) mainly limited to handling liquids, for example, a syringe carrying a liquid sample is introduced into many conventional gas chromatographs through a rubber septum, or (2) of the type that allows vapor-entrained samples to be introduced from sample tubes. However, the sample introduction means used in these methods must be designed specifically for the particular purpose of analysis. An example of this type of means is the Perkin Elmer Model ATD 50.TM. system, two-stage adsorber type gas chromatograph in which a sample is adsorbed onto an adsorbent material such as para-polyphenylene-oxide in the form of TENAX.TM. contained in a sample tube and then the sample is transferred to an adsorbent material in a second sample tube of different (usually smaller) dimensions from those of the first sample tube. A particular variant of this procedure is described by F. Raschdorf in Chimia 32, 1978. Raschdorf employs a needle method for the introduction of compounds into gas chromatographs. A 100 ml gas syringe is described by Raschdorf and is employed to draw a known volume of sample gas through a thick needle containing an adsorbent such as TENAX. This needle, which functions as a sample tube, is disconnected from the barrel of the syringe and then connected to a supply of carrier gas before being introduced into the gas chromatograph. While the needle of Raschdorf is useful, there are drawbacks in that (a) it requires a large barrelled syringe and adsorbent loaded needle as opposed to the more convenient and conventional sample tubes, (b) a carrier gas entrained sample flow rate of 14 cc/min, which is required to transfer the sample from the syringe to the gas chromatograph, is an order of magnitude too great to be handled by capillary chromatography columns of the type preferred for microanalysis, and (c) hardware modifications may be necessary in the sample introduction port of the chromatograph to accommodate the large needle that is used.
There is a need for a method and an apparatus for the introduction of a vaporizable sample into an analytical test apparatus which uses sample tubes of the conventional type, with the attendant advantages of choice of adsorption material that they allow, but which is also capable of matching the ideal flow for proper desorption through conventional sample tubes of about 30 cc/min., with the optimum flow for capillary gas chromatograph operations of 1-5 cc/min.